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고속 적외선 열화상 기법을 이용한 마이크로/나노구조표면에서의 미시적 비등 인자들의 측정
박영재(Youngjae Park),김형모(Hyungmo Kim),김준원(Joonwon Kim),김형대(Hyungdae Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
It is well known that nucleate boiling heat transfer and critical heat flux can be significantly enhanced by micro- and nano-scale structures of a boiling surface, which change the fundamental boiling parameters such as nucleation site density, dry area fraction and triple contact line density. In order to understand and model the physical mechanisms of the enhancements on a structured surface, it is required to measure such fundamental parameters. However, it is very challenging to detect the microscopic boiling parameters on structured surfaces using conventional measurement and visualization techniques for surface temperature and liquid-vapor phase distribution. In this study, a new visualization technique using infrared thermometry is presented to measure the microscopic boiling parameters on a boiling surface with micro- and nano-scale structures. The augmentations of boiling heat transfer coefficient and critical heat flux on the tested surfaces with different structures are interpreted with the change of microscopic boiling parameters.
YCbCr 공간에서 눈 영역의 피부색을 이용한 피부영역 검출 기법
박영재(YoungJae Park),김계영(GyeYoung Kim),최형일(HyungIl Choi) 한국정보과학회 2009 정보과학회 컴퓨팅의 실제 논문지 Vol.15 No.7
입력된 영상을 유해영상인지 아닌지 판단하기 위해 여러 가지 방법이 사용 될 수 있다. 현재, 대부분의 유해영상검출에 대한 연구는 피부색상이 전체영상에서 차지하는 비율에 기반하고 있다. 본 논문에서는 YCbCr에서 피부영역을 검출 하는 기법을 제안한다. 피부영역은 YCbCr에서 특징적인 분포를 나타내는데 이를 이용하여 배경영역과 피부영역을 분리하고자 한다. 먼저 Eye-Map을 이용하여 눈의 영역을 찾은 후 그 주변 영역의 색상을 이용해 피부영역의 색상값 분포를 찾고, 전체 영상에서 그 분포와 근거리에 있는 영역들을 피부영역으로 검출하는 방식이 된다. There are many ways to judge whether the input image is adult-image or not. Until now, adultimage detection has been examined by the ratio of skin area in full image. In this paper, we propose a method to extract skin region in YCbCr. Skin region shows unique distribution in YCbCr, and we will separate the skin region from background using the distribution. First, we are going to find Eye zone using Eye-Map. Then we will find out the color value for the distribution of skin region using the color of Eye zone. Next, we will find the distribution of the area through the skin region in full-image.
단일 가열봉의 재관수 시 2상유동 및 벽면 열전달에 관한 실험적 연구
박영재(Youngjae Park),김형대(Hyungdae Kim) 한국가시화정보학회 2020 한국가시화정보학회지 Vol.18 No.3
Two-phase flow and heat transfer characteristics during the reflood phase of a single heated rod in the KHU reflood experimental facility were examined. Two-phase flow behavior during the reflooding experiment was carefully visualized along with transient temperature measurement at a point inside the heated rod. By numerically solving one-dimensional inverse heat conduction equation using the measured temperature data, time-resolved wall heat flux and temperature histories at the interface of the heated rod and coolant were obtained. Once water coolant was injected into the test section from the bottom to reflood the heated rod of >700°C, vast vapor bubbles and droplets were generated near the reflood front and dispersed flow film boiling consisted of continuous vapor flow and tiny liquid droplets appeared in the upper part. Following the dispersed flow film boiling, inverted annular/slug/churn flow film boiling regimes were sequentially observed and the wall temperature gradually decreased. When so-called minimum film boiling temperature reached, the stable vapor film between the heated rod and coolant was suddenly collapsed, resulting in the quenching transition from film boiling into nucleate boiling. The moving speed of the quench front measured in the present study showed a good agreement with prediction by a correlation in literature. The obtained results revealed that typical two-phase flow and heat transfer behaviors during the reflood phase of overheated fuel rods in light water nuclear reactors are well reproduced in the KHU facility. Thus, the verified reflood experimental facility can be used to explore the effects of other affecting parameters, such as CRUD, on the reflood heat transfer behaviors in practical nuclear reactors.